Milling machines have been around for a long time, and are used to machine solid materials such as wood or metal. Milling machines can perform numerous operations, from simple cutting, such as slot and keyway cutting, planing or drilling, to more complex functions, such as contouring and die sinking. Quite often, fluid is sprayed or pumped to the material being cut to cool and lubricate the cutting device and to wash away the material being cut away. Milling machines range in size from small, bench-mounted devices to room-sized machines.
Milling machines may be operated manually, mechanically automated, or digitally automated using computer numeric control. As such, depending on the type of operation, the movement of the material and the cutter can be precisely controlled to less than 0.001 in (0.025 mm).
Milling machines are often classed in two basic types, horizontal and vertical, referring to the orientation of the main shaft of the machine. Whereas a drill press holds the material to be cut or drilled stationary in relation to the drill, milling machines may move the material in relation to the cutting device. Thus, the cutting device can cut the material from its side as well as the tip.
For vertical milling machines, the shaft or axis is vertically oriented and the cutter is held in the spindle and rotates on its axis. The spindle can generally be extended or the table can be moved, obtaining the same result. Generally, the vertical milling machines can be a bed mill or a turret mill. The turret mill has a stationary spindle and the table can be moved perpendicular and parallel during the milling or cutting. The bed mill, on the other hand, only provides for a perpendicular movement in relation to the spindle, while the spindle moves parallel to its own axis.
A mill-drill is another milling machine, which is usually smaller in size. The mill-drill is similar to a small drill press but equipped with an X-Y table.
A horizontal mill has a similar x-y table, but the cutters are mounted horizontally across the table. Horizontal mills can also include a built-in rotary table that allows milling at various angles. While the tools available to a vertical mill may be used in a horizontal mill, horizontal mills can also use arbor-mounted cutters, such as side and face mills. These cutters have a cross section similar to a circular saw, but are generally wider and smaller in diameter. Since the cutters have good support from the arbor and a larger cross-sectional area, heavier cuts can be taken speeding up the removal of material.
Further, in order to automatically control a milling machine (as opposed to manual control), a milling machine can be connected to and controlled by a Computer Numeric Control or CNC system. The CNC system provides for precise and/or repetitive control of the machine. Most CNC milling machines are computer controlled vertical mills with the ability to move the spindle vertically along the Z-axis. This extra degree of freedom permits their use in die sinking, engraving applications, milling sculptures, etc. Milling precision can also be improved when CNC is combined with certain cutting tools, such as conical or ball nose cutters.
A retrofit kit can be used to convert a manual milling machine to an automatic milling machine, however one drawback occurs when the original acme nut is removed in order to replace with ball screws and nuts. The original acme nuts are preconfigured and aligned by the manufacturer for each specific machine. A complete ball nut replacement would need to have the same configuration and alignment which would require custom machining and tedious alignment for each machine.
As such, there currently exists a need for a retrofit kit that can simply and quickly retrofit a milling or drilling machine into a CNC milling machine that can be computer controlled for more precise milling and drilling operations, without removing the original acme nut.